1. Field of the Invention
One aspect of the present invention is directed at plastic support net for filter media.
2. Background Art
Filter medium is often subjected to a pleating operation to form pleated filter material having a greater filtration surface area than the unpleated filter medium. The increased filtration surface area allows the pleated filter medium to remove a relatively higher amount of particulates, e.g. dirt and dust, from a fluid flow, e.g. air, through the filter medium. Moreover, pleating the filter medium reduces the face velocity of the fluid across the medium, thereby reducing pressure drop and/or energy use.
Many pleated filter medium require a support structure to hold the filter material in a pleated shape, thereby maintaining the increased filtration surface area. Typically, a filter medium assembly is made using the following process: (1) a relatively flat support structure is layered onto a flat filter medium, or vice versa, to obtain a flat filter assembly; and (2) the flat filter assembly is subsequently pleated to obtain a pleated filter assembly. For many filter medium, step (2) is carried out at ambient temperatures because an elevated temperature pleating process may damage the filter medium material and/or ambient temperature pleating can be less expensive and/or more efficient than elevated temperature pleating.
Currently, metal mesh materials are utilized as pleated support structures that can be formed at ambient temperatures. While metal mesh materials have this advantage, pleated filter assemblies formed with such support material cannot be fully incinerated because of the metal mesh support material. Moreover, the sharp points and edges formed while pleating the metal mesh material can be difficult to handle. Furthermore, metal mesh is susceptible to rusting and corrosion.
Alternatively, polypropylene (PP) has been utilized as an incinerable pleated filter support material. However, polypropylene must be pleated at an elevated temperature to take and hold a pleat, which can cause damage to heat sensitive filter medium materials. For example, the filter medium can be made of a mixture of PP and polyethylene (PE) fibers, which is processed in a heated through-air bonder machine to tackify and melt the PE fibers, thereby consolidating the nonwoven filter medium material. Further heating during a pleating operation can degrade the filtration characteristics of the medium. Other examples of filter support materials that are heated to take on a pleat include nylons and polyesters used with hydrocarbon liquid filter medium. As with the PP/PE mixture filter medium example, heating of the hydrocarbon liquid filter medium during the pleating operation can degrade the filtration characteristics of the filter medium.
In light of the foregoing, what is needed is a support structure for supporting filter media that overcomes one or more of the shortcomings identified above. What is further needed is a pleated filter assembly and method of forming the same under ambient conditions that overcome one or more of the shortcomings identified above.